Thousands of hardline Muslims have rallied in Jakarta in protest against the city’s ethnic Chinese and Christian governor, further fuelling ethnic tensions ahead his re-election bid in February.

Governor Basuki Tjahaja Purnama, better known by his nickname “Ahok”, became Jakarta’s first ethnic Chinese governor in 2014, but hardline Muslims have opposed his rise to power.

Dressed in white, thousands of members of several hardline groups chanted anti-Ahok slogans surrounded by tight military and police security, but the demonstration last Friday was otherwise generally peaceful.

Speaking on the sidelines of the demonstration, Forum Umat Islam Secretary General Muhammad al Khaththath didn’t single out Purnama, but said leaders should be Muslim “because that is what the Koran calls for.”

Ahok has gained a reputation for being a tough reformer, and has recently come under attack from Muslim groups for comments about the Koran.

The organiser of Friday’s protest, the hardline Islamic Defenders Front, is known for violent protests and attacks against minorities around the country since its creation in 1999. It has also frequently protested over Purnama.

However, FPI is small compared with Indonesia’s biggest Islamic group, the moderate Nahdlatul Ulama, which has about 40 million members.

Ahmad Ishomuddin, a senior official at Nahdlatul Ulama, told Reuters that his organisation did not support the protest, and that violence went against religious teachings.

“This could be dangerous,” Ishomuddin said, urging Muslims to remain calm and to forgive Purnama over the recent comments.

“Ahok, whose tongue slipped, has apologised.”

Indonesia is the world’s largest Muslim-majority nation, priding itself as a peacemaker, and the vast majority of its population practise a moderate form of the religion.

Indonesia also has a large ethnic Chinese minority, many of whom are Buddhist. The country has a history of anti-Chinese violence, most sharply in the late 1990s amid the political and economic crisis that brought down authoritarian ruler Suharto.

In July, authorities detained seven people on suspicion of attacking several Buddhist temples in Sumatra.